1. Technical Field of the Invention
The present invention relates to a route guidance system, and more particularly to a route guidance system composed of a navigation apparatus mounted on a car and a center apparatus to communicate with a plurality of navigation apparatuses.
2. Related Art (Background Art)
A navigation apparatus to guide a driver on a traveling route to its destination is widely spread. Such a navigation apparatus is provided with data related to a destination which may be an object of guidance, road data for searching and finding a traveling route to a destination and map data for drawing a map, and searches and finds a route from the present place to the destination using road information and performs guidance in the direction to travel (to go straight or to change the direction of progress) according to the present position and the found route while detecting the present position of the car by means of a GPS receiver and the like.
In order to make it possible to set a destination in various manners based on a telephone number, the name of a facility, a genre, an address and the like, such a navigation apparatus needs to be provided with detailed destination data related to destinations as well as road data of various information such as the number of lanes, a road width, one-way street, no right-turn, no entry and the like for each intersection and road, and therefore, is made to store enormous data in it.
On the other hand, recently, a communication navigation system in which a navigation apparatus at the car side is provided with minimum data and takes charge of detection of the present place and a traveling route guidance, and a process of finding a route to a destination is performed collectively by a given information center has been developed. In such a system, a driver receives a traveling route found to its destination, map data and the like from an information center by means of a radio communication means such as a car telephone, a mobile telephone, a PHS (personal handyphone system) or the like connected to a navigation apparatus.
According to such a communication navigation system, it is not necessary for a navigation apparatus to keep map data, destination data and road data for route finding, and such a process requiring a great amount of computation as a route finding process becomes unnecessary, and thus it becomes possible to perform more rapidly other processes thanks to reduction of the burden on a controller.
The inventors of the present application have known that functions required by a user such as a driver or the like are different according to the purpose or state of traveling.
That is to say, in case of traveling by car, a user most frequently travels around its home or company, or travels repeatedly in the same certain local area. In such a case, it is possible for the user to reach properly its destination even if the user does not take the trouble of receiving a route guidance by voice according to its traveling route found by setting its destination and finding the route. For example, in case of knowing the location of its destination such as a department store, an amusement park, a golf course, a branch office, a customer's office and the like, a route guidance is naturally unnecessary, and if its destination is near around a road along which the user has traveled, it is enough for the user to make it possible to confirm the present position of its car on a screen after it has traveled near around its destination.
And a case that the user needs to be guided on the route to its destination is limited to a case that the user is a sheer stranger about its destination and peripheral area, a case that the route to its destination is complicated, and the like, and in such a case a route guidance to the destination is an indispensable function, but the number of such travels is relatively less in comparison with the total number of travels (total number of actions of taking a car).
In such a way, functions required when a driver travels by car are different according to the state of traveling or its destination, but since up to now a navigation apparatus and a communication navigation system are composed regardless of such a purpose or condition of traveling of a driver, a conventional navigation apparatus has unnecessary functions and many portions being poor in efficiency of use.
That is, in case of assuming the maximum possible functions and processes for navigation and implementing these functions on a navigation apparatus at the car side, since destinations to be set or roads to be searched and found are intended for a wide specific area, for example, the whole country (whole Japan, whole United State of America, whole Germany, etc.), destination data and road data become enormous and a destination setting process or a route finding process is performed on the basis of an enormous amount of data and therefore there is a problem that a great amount of computation and a long time of computation are needed and the burden on a controller to perform these processes are heavy. And since road data vary always due to completion of a new road, or new setting or changing of "no right-turn", "no left-turn" or the like, each navigation apparatus needs to update such road data.
On the other hand, in case of a communication navigation system, there is an advantage that such a burden on a controller as a data storage or a high-degree process is lightened, but there is a problem that communication with an information center needs to be frequently performed communication expenses become large and a time of reception becomes longer due to the increase of the amount of data to be received from an information center because of reduction of data kept in a car.
Thereupon, the present invention has been performed in order to solve such existing problems, and aims at providing a route guidance systen more suitable for the purpose or state of traveling of a user in which data to be stored and functions to be performed are properly shared between a navigation apparatus mounted on a car and a center apparatus.